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Coolant in oil. Need help identifying cause.

3141 Views 84 Replies 14 Participants Last post by  eric32
This is sort of related to my other post regarding a cam swap. In the process of learning more about that process, it was discovered that the dumped oil contains a good amount of coolant. The results of the oil test can be found here. Suffice it to say, there is coolant in the oil. So I am now taking a detour on my way to a different cam as this issue will have to be addressed first.

I am looking for help identifying where the coolant may be seeping into the oil. I will do a pressure test tomorrow, but for now I have pulled the spark plugs out and stuck an endoscope into all the cylinders. The results are below. Note that the truck has not been driven or started in about 3 days prior to my doing this work.
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Here are some picture from the endoscope. All pistons look about the same - pretty carboned up. Some, however, have what appears to be moisture. Can you guy draw any conclusions?

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Whichever cylinder the clean spark plug came out of is probably the cylinder taking coolant. Note the borescope photo of that cylinder is one of the missing from your collection.

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I don’t see any way around prying the top end off the block.

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cylinder 5’s sparking bolt is as clean as it came out of the box this is prime evidence that it is being steam cleaned. This is one of the things that is clue to coolant, primarily water, getting into the cylinder as it operates that we look for.

It tends to be head gasket failures, cylinder head in the combustion chamber cracks between exhaust and intake or between eithe valve and spark plug boss. Also, in the ports especially if the head has been ported.

Operating is different from not, the heat and the load dynamics can and do open these wounds that otherwise can’t be seen without either a Magnaflux on iron or Zyglo on either Iron or aluminum.

This rationale suggests that if I do a leak down test on that cylinder, it will ALSO need to be performed at operating temp. I am already imagining trying to find TDC on #5 and then plugging the tester finagling around the scalding block and headers. Seems like it would be easier to just pull the damn head off and just look for any sign of trouble.
I think myself and others already suggest pulling the head. It’s probably going to have to be tested by Magnaflux or Ziglo to find the crack if it isn’t a gasket problem.

There is no doubt at this point that I will be tearing into this engine in short order. But I did notice another oddity and wanted to ask yall about it. Check out this gap between the intake manifold and intake port on cylinder 1. And yes, that's a feeler gauge on the second picture buried in there. It's a 0.015 gap. Wouldn't this create a big vacuum leak? At least for cylinder one?
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Are you indicating that the gasket and the intake don’t cover the port roof? If so that is an air leak.

So let’s chase this a little further.

Vacuum leaks typically cause a fast idle with little control from resetting the curb idle and don’t do well with reducing fuel flow from the idle mixture screws.

Generally manifold vacuum is down.

Number 5 could be dried fried, but usually an air leak in one place is felt everywhere.

Fitment, not going to go back and hunt for your other inputs, so how about going back over what heads and whether they were milled, ported, etc. What intake and gasket set if known? Whether the block has been decked?

The intake bolts like the head bolts penetrate into the cooling jackets. The powder that came out with the intake bolts was either corrosion from coolant leakage or the failed remainder of some sort of sealer. The intake and cylinder head fastener holes are open to the cooling passages or in the intake case some open into oily places so must use a sealer on the threads that is proof against failure by coolant which carry's either some sort of glycol ethylene or propylene being the most common which is a solvent material and contains an Inorganic Acid Technology or the an Organic Acid Technology (OAT) like original Dexcool or Hybred Organic Acid Technology that the Euros and Asians like but these are not the same mix where Euro HOAT uses a silicate base which is good where people introduce hard water into the cooling system while the Asian’s use a phosphate inhibitor that is intolerant of the chemistry of hard water so this coolant must be blended with distilled or deionized water. Which really should be used in all coolant solutions, not the stuff from your house’s or a gas station’s water tap. All of these chemistries have differing reactions and consumable additive life times. So it’s easy to find corrosion or deposition products with fasteners which often are plated thus developing other reaction in their joints. Note for Chevrolet and others that you don’t find plated fasteners on or in the engine because the plating provides another reactant in the joint.

Teflon tape is really meant to seal plumbing threads which in the US are a tapered thread where bolted joints are a straight thread. To a large extent straight threads seal better with paste sealer than tape, though Chevy puts a Teflon coating on their head bolts but is usually damaged by the time you get them. In the past and to some extent I still use Teflon based or infused plumbers thread sealer. But I find it’s not always resistant to constant exposure to engine coolant or oil and is certainly unsuitable for solvent fuels like gasoline. I’ve pretty much returned to old fashion Permatex No 2 or 3 as it doesn’t depend on a cure to form a washout resistant thread seal and it’s lubricity is close to 30 wt engine oil which is used as the thread lubrication material for most stated fastener torque tables You may assume this is true unless otherwise stated. This establishes the ratio of torque applied to stretch achieved when tightening a fastener. So changes in the lubricity within the threads from bare to moly or Teflon or RTV in the joint changes the torque applied to stretch achieved ratio.

So you need a sealer and lubricant in the bolted joints that is resistant to coolant and oil while sealing straight threads and providing thread lubricity that acts like 30 wt engine oil all at the same time.

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390 horsepower is a measure of work accomplished. The result would be the same assuming the gearing of each engine was favorable to where that power appears on the RPM curve.

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